Cost-effectiveness of hydrotherapy versus land-based therapy in patients with musculoskeletal disorders in Singapore

Cost-effectiveness of hydrotherapy versus land-based therapy in patients with musculoskeletal... Abstract Background The study evaluated the cost-effectiveness of hydrotherapy versus land-based therapy in patients with musculoskeletal disorders (MSDs) in Singapore. Methods A decision-analytic model was constructed to compare the cost-effectiveness of hydrotherapy to land-based therapy over 3 months from societal perspective. Target population comprised patients with low back pain (LBP), osteoarthritis (OA), rheumatoid arthritis (RA), total hip replacement (THR) and total knee replacement (TKR). Subgroup analyses were carried out to determine the cost-effectiveness of hydrotherapy in individual MSDs. Relative treatment effects were obtained through a systematic review of published data. Results Compared to land-based therapy, hydrotherapy was associated with an incremental cost-effectiveness ratio (ICER) of SGD 27 471 per quality-adjusted life-year (QALY) gained, which was below the willingness-to-pay threshold of SGD 70 000 per QALY (one gross domestic product per capita in Singapore in 2015). For the respective MSDs, hydrotherapy were dominant (more effective and less costly) in THR and TKR, cost-effective for LBP and RA, and not cost-effective for OA. Treatment adherence and cost of hydrotherapy were key drivers to the ICER values. Conclusions Hydrotherapy was a cost-effective rehabilitation compared to land-based therapy for a population with MSDs in Singapore. However, the benefit of hydrotherapy was not observed in patients with OA. cost-effective analysis, economic model, hydrotherapy, low back pain, musculoskeletal diseases Introduction Musculoskeletal disorders (MSDs) refer to a variety of conditions affecting bones, joints and muscles. The burden of MSDs is significant in terms of treatment, the impact on quality of life and productivity. The annual cost for treatment and lost wages associated with MSDs in the United States (US) was USD 213 billion,1 while across the European countries, MSDs accounted for 53% of all work-related diseases incurring €240 billion.2 According to the Global Burden of Disease Study 2016, low back pain (LBP) was the leading cause of disability especially in developed countries.3 As such, effective treatment strategies are crucial to reduce MSD-related financial burden for patients as well as healthcare system. Although MSDs are generally nonfatal, the debilitating nature can lead to deterioration of patients’ function and quality of life. Rehabilitation plays an important role in the management of patients with MSDs. Land-based physiotherapy ranging from patient education to exercise has been shown to be effective in reducing pain and improving patients’ function.4 There has been a growing body of evidence to support the use of hydrotherapy in chronic musculoskeletal conditions.5–8 Compared to land-based physiotherapy, hydrotherapy utilizes the unique properties of water to reinforce rehabilitative efforts by enhancing relaxation, decreasing pain, improving strength and helping with balance. Both hydrotherapy and land-based therapy have shown benefits in the treatment of MSDs including chronic LBP, osteoarthritis (OA) and rheumatoid arthritis (RA).9–11 Besides the standard benefits of land-based exercise such as increased muscle strength, improved aerobic and cardiovascular capacity, the buoyancy of water may reduce the risk of muscle or joint injury associated with exercise. Because of this advantage, hydrotherapy is suggested as an initial treatment option for patients requiring early rehabilitation such as post-surgery.12 Given the relatively high operating cost for an in-house pool, hydrotherapy is not adopted as a routine clinical practice in most healthcare facilities. Apart from a paucity of cost-effectiveness data on hydrotherapy compared to land-based therapy, published cost-effectiveness findings have been inconsistent. Hydrotherapy was reported as a cost-effective rehabilitation when compared to usual care in patients with OA in the United Kingdom (UK), with an incremental cost-effectiveness ratios (ICERs) ranging from £3838 to £5951 per quality-adjusted life-year (QALY), well below the UK National Institute for Health and Care Excellence (NICE) threshold of £20 000 per QALY gained.13 On the other hand, hydrotherapy did not achieve a better outcome and reduced cost compared with usual care in the USA.14 Given that the differing conclusions could be due to different healthcare settings and costs of treatment, we evaluated the cost-effectiveness of hydrotherapy versus land-based therapy in patients with MSDs comprising LBP, OA, RA, total hip replacement (THR) and total knee replacement (TKR) in Singapore. We also identified which particular musculoskeletal conditions would benefit most from hydrotherapy. Methods Model overview A decision-analytic model in the form of a decision tree was developed to estimate the societal cost and QALY of a cohort of patients with MSDs receiving hydrotherapy or land-based therapy (Fig. 1). The target population comprised of patients with LBP, OA, RA, THR and TKR; and the distribution of these conditions was estimated from a real-world patients (n = 23 440) seeking rehabilitation in a public hospital in Singapore in 2014. The relative distributions of the different types of MSDs were: LBP (93.49%), OA (3.0%), RA (0.73%), THR (0.59%) and TKR (2.18%). Both THR and TKR received rehabilitation services in an inpatient setting while treatment for LBP, OA and RA were provided on an outpatient basis. These proportions representing the disease profile of the target cohort were inputted into the model to reflect real-world setting. In addition, the model was structured to reflect the utilization pattern of hydrotherapy and land-based therapy in Singapore. Patients with THR and TKR were modelled as post-operative rehabilitation in inpatient setting while patients with LBP, OR and RA were treated in outpatient setting. Fig. 1 View largeDownload slide Schematic representation of model structure. Fig. 1 View largeDownload slide Schematic representation of model structure. The model duration was set as 3 months considering the disease heterogeneity of the target cohort and duration of most rehabilitation programmes ranged from 4 to 12 weeks.5,6,9,11,15–18 During this time horizon, the model was expected to capture the clinical benefit of the treatment while maintaining homogeneity of the outputs, which are cost and QALYs across the different MSDs. This ensures the validity of the final composite outcomes from a combination of condition-specific outputs for the entire cohort. A longer time horizon would require more assumptions on the clinical outcomes for individual MSDs which in turn may introduce greater uncertainties and probability of biases in the model. Treatment benefits were reflected in terms of an improvement in quality of life and achievement of treatment goal as informed by literature. As rehabilitation therapy is generally safe and in view of the relatively short modelling period,12 the model did not include adverse events. Premature termination of treatment has been reported for both hydrotherapy and land-based therapy and this non-adherence has implication on the cost-effectiveness of the treatments.19 Therefore, we modelled the impact of non-adherence for patients with LBP,5,15 OA13,14 and RA6,11 and assumed patients with THR and TKR to be fully compliant given the inpatient setting. Total societal cost and QALYs for hydrotherapy and land-based therapy were estimated by the model. Discounting was not applied considering the relatively short model duration. An ICER represents the incremental cost incurred for each additional QALY gained by hydrotherapy as compared to land-based therapy. The cost-effectiveness threshold or willingness-to-pay was set as SGD 70 000 (one gross domestic product per capita in Singapore in 2015) following the World Health Organization’s recommendation.20 An ICER below this threshold indicates that the treatment is cost-effective compare to the baseline comparator in Singapore. The model was developed and analysed using TreeAge Pro Suite software 2016 (Williamstown, MA, USA). Cost We adopted a societal perspective by including both direct and indirect cost involved in the provision of rehabilitative treatment in Singapore. The cost in our model represented the societal economic burden in providing the two rehabilitation strategies in Singapore. Direct medical cost included cost of treatment, hospitalization and therapist visits, which was estimated by a micro-costing approach by multiplying unit price with the amount of resource consumed. We obtained healthcare resource use and cost data from hospital database (Table 1). Non-medical cost included transportation fees during treatment period that were based on data from the Land Transport Authority in Singapore.21,22 Given that the cohort comprised of a substantial proportion of outpatients (LBP, OA and RA), we also incorporated indirect cost as measured by absenteeism for seeking rehabilitation. The associated productivity loss was the product of national mean salary and duration of absenteeism,23,24 following the human capital approach. Costs were calculated in Singapore dollars (1 Singapore dollar = 0.72 US dollars as of November 2016). Table 1 Cost estimates based on resource consumption for hydrotherapy and land-based therapy Cost components Land-based therapy Hydrotherapy Source Point estimate Range Distribution Point estimate Range Distribution Direct cost  Rehabilitation cost   Cost per session (SGD)    Total hip replacement 99 NA NA 110 NA NA Hospital    Total knee replacement 99 NA NA 110 NA NA Hospital    Low back pain 60 NA NA 78 NA NA Hospital    Osteoarthritis 60 NA NA 78 NA NA Hospital    Rheumatoid arthritis 60 NA NA 78 NA NA Hospital   Treatment frequency (weekly sessions)    Total hip replacement 5 NA NA 5 NA NA Hospital    Total knee replacement 5 NA NA 5 NA NA Hospital    Low back pain 1.5 (1–2) Triangular 1.5 (1–2) Triangular Hospital    Osteoarthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital    Rheumatoid arthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital   Treatment duration (week)    Total hip replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Total knee replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Low back pain 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Osteoarthritis 4 NA NA 4 NA NA Hospital    Rheumatoid arthritis 4 NA NA 4 NA NA Hospital   Hospital stay (day)    Total hip replacement 35 (14–55) Triangular    Total knee replacement 22 (5–28) Triangular   Reduction in hospital stay 0 0 NA 1 (0–2) Triangular (12)   Daily cost of hospitalization (SGD) 402 NA NA 402 NA NA Hospital  Post-discharge rehabilitation   Number of sessions    Total hip replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital    Total knee replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital   Cost per session (SGD) 110 NA NA 80 NA NA Hospital  Transport cost (SGD) 8.3 (7.8–8.7) Triangular 8.3 (7.8–8.7) Triangular (21) Indirect cost  Percentage of working patients (%)   Low back pain 56 55–57 Beta 56 55–57 Beta Hospital   Osteoarthritis 51 43–60 Beta 51 43–60 Beta Hospital, (23)   Rheumatoid arthritis 44 41–47 Beta 43.5 41–47 Beta (24)  Disease-specific absenteeism (day)   Osteoarthritis 28 NA NA 28 NA NA Hospital   Rheumatoid arthritis 28 NA NA 28 NA NA Hospital   Low back pain 25 NA NA 25 NA NA Hospital  Daily cost of productivity loss (SGD) 124 NA NA 124 NA NA (23) Cost components Land-based therapy Hydrotherapy Source Point estimate Range Distribution Point estimate Range Distribution Direct cost  Rehabilitation cost   Cost per session (SGD)    Total hip replacement 99 NA NA 110 NA NA Hospital    Total knee replacement 99 NA NA 110 NA NA Hospital    Low back pain 60 NA NA 78 NA NA Hospital    Osteoarthritis 60 NA NA 78 NA NA Hospital    Rheumatoid arthritis 60 NA NA 78 NA NA Hospital   Treatment frequency (weekly sessions)    Total hip replacement 5 NA NA 5 NA NA Hospital    Total knee replacement 5 NA NA 5 NA NA Hospital    Low back pain 1.5 (1–2) Triangular 1.5 (1–2) Triangular Hospital    Osteoarthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital    Rheumatoid arthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital   Treatment duration (week)    Total hip replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Total knee replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Low back pain 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Osteoarthritis 4 NA NA 4 NA NA Hospital    Rheumatoid arthritis 4 NA NA 4 NA NA Hospital   Hospital stay (day)    Total hip replacement 35 (14–55) Triangular    Total knee replacement 22 (5–28) Triangular   Reduction in hospital stay 0 0 NA 1 (0–2) Triangular (12)   Daily cost of hospitalization (SGD) 402 NA NA 402 NA NA Hospital  Post-discharge rehabilitation   Number of sessions    Total hip replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital    Total knee replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital   Cost per session (SGD) 110 NA NA 80 NA NA Hospital  Transport cost (SGD) 8.3 (7.8–8.7) Triangular 8.3 (7.8–8.7) Triangular (21) Indirect cost  Percentage of working patients (%)   Low back pain 56 55–57 Beta 56 55–57 Beta Hospital   Osteoarthritis 51 43–60 Beta 51 43–60 Beta Hospital, (23)   Rheumatoid arthritis 44 41–47 Beta 43.5 41–47 Beta (24)  Disease-specific absenteeism (day)   Osteoarthritis 28 NA NA 28 NA NA Hospital   Rheumatoid arthritis 28 NA NA 28 NA NA Hospital   Low back pain 25 NA NA 25 NA NA Hospital  Daily cost of productivity loss (SGD) 124 NA NA 124 NA NA (23) NA, not applicable. Table 1 Cost estimates based on resource consumption for hydrotherapy and land-based therapy Cost components Land-based therapy Hydrotherapy Source Point estimate Range Distribution Point estimate Range Distribution Direct cost  Rehabilitation cost   Cost per session (SGD)    Total hip replacement 99 NA NA 110 NA NA Hospital    Total knee replacement 99 NA NA 110 NA NA Hospital    Low back pain 60 NA NA 78 NA NA Hospital    Osteoarthritis 60 NA NA 78 NA NA Hospital    Rheumatoid arthritis 60 NA NA 78 NA NA Hospital   Treatment frequency (weekly sessions)    Total hip replacement 5 NA NA 5 NA NA Hospital    Total knee replacement 5 NA NA 5 NA NA Hospital    Low back pain 1.5 (1–2) Triangular 1.5 (1–2) Triangular Hospital    Osteoarthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital    Rheumatoid arthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital   Treatment duration (week)    Total hip replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Total knee replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Low back pain 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Osteoarthritis 4 NA NA 4 NA NA Hospital    Rheumatoid arthritis 4 NA NA 4 NA NA Hospital   Hospital stay (day)    Total hip replacement 35 (14–55) Triangular    Total knee replacement 22 (5–28) Triangular   Reduction in hospital stay 0 0 NA 1 (0–2) Triangular (12)   Daily cost of hospitalization (SGD) 402 NA NA 402 NA NA Hospital  Post-discharge rehabilitation   Number of sessions    Total hip replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital    Total knee replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital   Cost per session (SGD) 110 NA NA 80 NA NA Hospital  Transport cost (SGD) 8.3 (7.8–8.7) Triangular 8.3 (7.8–8.7) Triangular (21) Indirect cost  Percentage of working patients (%)   Low back pain 56 55–57 Beta 56 55–57 Beta Hospital   Osteoarthritis 51 43–60 Beta 51 43–60 Beta Hospital, (23)   Rheumatoid arthritis 44 41–47 Beta 43.5 41–47 Beta (24)  Disease-specific absenteeism (day)   Osteoarthritis 28 NA NA 28 NA NA Hospital   Rheumatoid arthritis 28 NA NA 28 NA NA Hospital   Low back pain 25 NA NA 25 NA NA Hospital  Daily cost of productivity loss (SGD) 124 NA NA 124 NA NA (23) Cost components Land-based therapy Hydrotherapy Source Point estimate Range Distribution Point estimate Range Distribution Direct cost  Rehabilitation cost   Cost per session (SGD)    Total hip replacement 99 NA NA 110 NA NA Hospital    Total knee replacement 99 NA NA 110 NA NA Hospital    Low back pain 60 NA NA 78 NA NA Hospital    Osteoarthritis 60 NA NA 78 NA NA Hospital    Rheumatoid arthritis 60 NA NA 78 NA NA Hospital   Treatment frequency (weekly sessions)    Total hip replacement 5 NA NA 5 NA NA Hospital    Total knee replacement 5 NA NA 5 NA NA Hospital    Low back pain 1.5 (1–2) Triangular 1.5 (1–2) Triangular Hospital    Osteoarthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital    Rheumatoid arthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital   Treatment duration (week)    Total hip replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Total knee replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Low back pain 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Osteoarthritis 4 NA NA 4 NA NA Hospital    Rheumatoid arthritis 4 NA NA 4 NA NA Hospital   Hospital stay (day)    Total hip replacement 35 (14–55) Triangular    Total knee replacement 22 (5–28) Triangular   Reduction in hospital stay 0 0 NA 1 (0–2) Triangular (12)   Daily cost of hospitalization (SGD) 402 NA NA 402 NA NA Hospital  Post-discharge rehabilitation   Number of sessions    Total hip replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital    Total knee replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital   Cost per session (SGD) 110 NA NA 80 NA NA Hospital  Transport cost (SGD) 8.3 (7.8–8.7) Triangular 8.3 (7.8–8.7) Triangular (21) Indirect cost  Percentage of working patients (%)   Low back pain 56 55–57 Beta 56 55–57 Beta Hospital   Osteoarthritis 51 43–60 Beta 51 43–60 Beta Hospital, (23)   Rheumatoid arthritis 44 41–47 Beta 43.5 41–47 Beta (24)  Disease-specific absenteeism (day)   Osteoarthritis 28 NA NA 28 NA NA Hospital   Rheumatoid arthritis 28 NA NA 28 NA NA Hospital   Low back pain 25 NA NA 25 NA NA Hospital  Daily cost of productivity loss (SGD) 124 NA NA 124 NA NA (23) NA, not applicable. Health outcomes The outcome of interest was QALY gained that incorporates utility and quantity of life lived. Utilities in our model were represented by the EQ-5D scores, which measure preferences for health state ranging from 0 (death) to 1 (perfect health). The EQ-5D scores were derived from a systematic literature search using PubMed up to September 2015 for studies comparing hydrotherapy versus land-based therapy in patients with LBP,5,15 OA,13,14 RA,6,11 THR12 and TKR.12,25 Where EQ-5D data were not reported, we transformed the original scores measured by other quality of life instruments into EQ-5D values following the validated mapping algorithm.26 Utility data based on generic quality of life instrument such as EQ-5D are ideal and preferred to estimate the QALY impact. However, the UK National Institute for Health and Clinical Excellence (NICE) has recognized that mapping using an algorithm to predict health state utility values based on other measures of health are a valid approach to derive utility values when EQ-5D data are not available.27 For a fair comparison, our model assumed that patients receiving hydrotherapy and land-based therapy had same pre-rehabilitation utility which was a pooled mean of EQ-5D for individual conditions (Table 2). The differential effects on the quality of life by hydrotherapy and land-based therapy were calculated as a utility gain after a full course of exercise programme. In the situation of non-adherence, patients were assumed to drop out halfway and as such the utility gain was assumed to be null for the entire modelling period. Table 2 Parameters representing clinical effectiveness for hydrotherapy and land-based therapy Conditions Land-based therapy Hydrotherapy Source Point estimate Range/95% CI Distribution Point estimate Range/95% CI Distribution Pre-rehabilitation utility  Total hip replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12)  Total knee replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12, 25)  Low back pain 0.68 (0.64–0.71) Normal 0.68 (0.64–0.71) Normal (5, 15)  Osteoarthritis 0.68 (0.64–0.72) Normal 0.68 (0.64–0.72) Normal (13, 14)  Rheumatoid arthritis 0.66 (0.60–0.72) Normal 0.66 (0.60–0.72) Normal (6, 11) Post-rehabilitation utility gain  Total hip replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12)  Total knee replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12, 25)  Low back pain 0 NA NA 0.128 (0.121–0.135) Normal (5, 15)  Osteoarthritis 0 NA NA 0.017 (0–0.034) Normal (13, 14)  Rheumatoid arthritis 0.003 (0.001–0.100) LogNormal 0.091 (0.074–0.108) Normal (6, 11) Non-adherence rate (%)  Low back pain 0 NA Beta 11.1 (4.9–20.7) Beta (5, 15)  Osteoarthritis 6.9 (4.9–9.3) Beta 7.7 (5.6–10.3) Beta (13, 14)  Rheumatoid arthritis 7.3 (2.4–16.1) Beta 14.7 (7.6–24.7) Beta (6, 11) Conditions Land-based therapy Hydrotherapy Source Point estimate Range/95% CI Distribution Point estimate Range/95% CI Distribution Pre-rehabilitation utility  Total hip replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12)  Total knee replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12, 25)  Low back pain 0.68 (0.64–0.71) Normal 0.68 (0.64–0.71) Normal (5, 15)  Osteoarthritis 0.68 (0.64–0.72) Normal 0.68 (0.64–0.72) Normal (13, 14)  Rheumatoid arthritis 0.66 (0.60–0.72) Normal 0.66 (0.60–0.72) Normal (6, 11) Post-rehabilitation utility gain  Total hip replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12)  Total knee replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12, 25)  Low back pain 0 NA NA 0.128 (0.121–0.135) Normal (5, 15)  Osteoarthritis 0 NA NA 0.017 (0–0.034) Normal (13, 14)  Rheumatoid arthritis 0.003 (0.001–0.100) LogNormal 0.091 (0.074–0.108) Normal (6, 11) Non-adherence rate (%)  Low back pain 0 NA Beta 11.1 (4.9–20.7) Beta (5, 15)  Osteoarthritis 6.9 (4.9–9.3) Beta 7.7 (5.6–10.3) Beta (13, 14)  Rheumatoid arthritis 7.3 (2.4–16.1) Beta 14.7 (7.6–24.7) Beta (6, 11) NA: not applicable. Table 2 Parameters representing clinical effectiveness for hydrotherapy and land-based therapy Conditions Land-based therapy Hydrotherapy Source Point estimate Range/95% CI Distribution Point estimate Range/95% CI Distribution Pre-rehabilitation utility  Total hip replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12)  Total knee replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12, 25)  Low back pain 0.68 (0.64–0.71) Normal 0.68 (0.64–0.71) Normal (5, 15)  Osteoarthritis 0.68 (0.64–0.72) Normal 0.68 (0.64–0.72) Normal (13, 14)  Rheumatoid arthritis 0.66 (0.60–0.72) Normal 0.66 (0.60–0.72) Normal (6, 11) Post-rehabilitation utility gain  Total hip replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12)  Total knee replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12, 25)  Low back pain 0 NA NA 0.128 (0.121–0.135) Normal (5, 15)  Osteoarthritis 0 NA NA 0.017 (0–0.034) Normal (13, 14)  Rheumatoid arthritis 0.003 (0.001–0.100) LogNormal 0.091 (0.074–0.108) Normal (6, 11) Non-adherence rate (%)  Low back pain 0 NA Beta 11.1 (4.9–20.7) Beta (5, 15)  Osteoarthritis 6.9 (4.9–9.3) Beta 7.7 (5.6–10.3) Beta (13, 14)  Rheumatoid arthritis 7.3 (2.4–16.1) Beta 14.7 (7.6–24.7) Beta (6, 11) Conditions Land-based therapy Hydrotherapy Source Point estimate Range/95% CI Distribution Point estimate Range/95% CI Distribution Pre-rehabilitation utility  Total hip replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12)  Total knee replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12, 25)  Low back pain 0.68 (0.64–0.71) Normal 0.68 (0.64–0.71) Normal (5, 15)  Osteoarthritis 0.68 (0.64–0.72) Normal 0.68 (0.64–0.72) Normal (13, 14)  Rheumatoid arthritis 0.66 (0.60–0.72) Normal 0.66 (0.60–0.72) Normal (6, 11) Post-rehabilitation utility gain  Total hip replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12)  Total knee replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12, 25)  Low back pain 0 NA NA 0.128 (0.121–0.135) Normal (5, 15)  Osteoarthritis 0 NA NA 0.017 (0–0.034) Normal (13, 14)  Rheumatoid arthritis 0.003 (0.001–0.100) LogNormal 0.091 (0.074–0.108) Normal (6, 11) Non-adherence rate (%)  Low back pain 0 NA Beta 11.1 (4.9–20.7) Beta (5, 15)  Osteoarthritis 6.9 (4.9–9.3) Beta 7.7 (5.6–10.3) Beta (13, 14)  Rheumatoid arthritis 7.3 (2.4–16.1) Beta 14.7 (7.6–24.7) Beta (6, 11) NA: not applicable. Subgroup analyses Subgroup analysis was conducted for individual musculoskeletal conditions to provide comprehensive insights into the value of hydrotherapy as compared to land-based therapy. Sensitivity analyses Deterministic sensitivity analyses where key model inputs were varied across their plausible ranges were carried out to identify influential parameters on cost-effectiveness. In deterministic sensitivity analysis, the value of each input parameter was varied one at a time to evaluate how this variation affects the results. The results were presented as a tornado diagram showing the relative importance of each parameter. Probabilistic sensitivity analysis evaluating the robustness of modelling conclusion was also conducted. The probabilistic sensitivity analysis takes into account the uncertainty of all model input parameters simultaneously and describes the implications of that uncertainty on cost-effectiveness results.28 The results were presented as a cost-effectiveness acceptability curve that showed the probability of hydrotherapy being a cost-effective treatment relative to land-based therapy at various willingness-to-pay thresholds. Results For the defined target cohort, the model projected that hydrotherapy incurred an additional cost of SGD 419 and yielded an additional 0.015 QALY, producing an ICER of SGD 27 471 per QALY gained compared to land-based therapy. The ICER value was well below the pre-defined threshold of SGD 70 000 per QALY for cost-effectiveness. The subgroup analysis demonstrated that the cost-effectiveness of hydrotherapy was heterogeneous across the five MSD conditions. Hydrotherapy was associated with a QALY gained of 0.002, and cost saving of SGD 107 for THR and SGD 106 for TKR, respectively. Hydrotherapy was cost-effective for LBP and RA with an ICER of SGD 30 250 and SGD 40 482 per QALY. However, it was not cost-effective for OA with an ICER of SGD 110 000 per QALY which was above one GDP per capita in Singapore in 2015 (Table 3). Table 3 Cost-effectiveness results Conditions Land-based therapy Hydrotherapy ICER (SGD per QALY gained) Cost (SGD) QALY gained Cost (SGD) QALY gained Total hip replacement 16 532 0.177 16 425 0.179 Dominanta Total knee replacement 11 373 0.177 11 267 0.179 Dominanta Low back pain 2116 0.156 2646 0.174 30 250 Rheumatoid arthritis 2469 0.152 2832 0.161 40 482 Osteoarthritis 2766 0.157 2966 0.159 110 000 Entire cohort 2642 0.157 3096 0.173 27 471 Conditions Land-based therapy Hydrotherapy ICER (SGD per QALY gained) Cost (SGD) QALY gained Cost (SGD) QALY gained Total hip replacement 16 532 0.177 16 425 0.179 Dominanta Total knee replacement 11 373 0.177 11 267 0.179 Dominanta Low back pain 2116 0.156 2646 0.174 30 250 Rheumatoid arthritis 2469 0.152 2832 0.161 40 482 Osteoarthritis 2766 0.157 2966 0.159 110 000 Entire cohort 2642 0.157 3096 0.173 27 471 aHydrotherapy dominated land-based therapy with more QALYs and less costly. QALY, quality-adjusted life-years; ICER, incremental cost-effectiveness ratio. Table 3 Cost-effectiveness results Conditions Land-based therapy Hydrotherapy ICER (SGD per QALY gained) Cost (SGD) QALY gained Cost (SGD) QALY gained Total hip replacement 16 532 0.177 16 425 0.179 Dominanta Total knee replacement 11 373 0.177 11 267 0.179 Dominanta Low back pain 2116 0.156 2646 0.174 30 250 Rheumatoid arthritis 2469 0.152 2832 0.161 40 482 Osteoarthritis 2766 0.157 2966 0.159 110 000 Entire cohort 2642 0.157 3096 0.173 27 471 Conditions Land-based therapy Hydrotherapy ICER (SGD per QALY gained) Cost (SGD) QALY gained Cost (SGD) QALY gained Total hip replacement 16 532 0.177 16 425 0.179 Dominanta Total knee replacement 11 373 0.177 11 267 0.179 Dominanta Low back pain 2116 0.156 2646 0.174 30 250 Rheumatoid arthritis 2469 0.152 2832 0.161 40 482 Osteoarthritis 2766 0.157 2966 0.159 110 000 Entire cohort 2642 0.157 3096 0.173 27 471 aHydrotherapy dominated land-based therapy with more QALYs and less costly. QALY, quality-adjusted life-years; ICER, incremental cost-effectiveness ratio. Based on the deterministic sensitivity analysis, none of the input parameters overturned the result that hydrotherapy was a cost-effective option, even though some parameters changed ICERs substantially. Among the 10 most influential parameters, 6 variables were related to LBP group (Fig. 2). This was within expectation because the majority (93.49%) of the target cohort was LBP patients. The most significant parameter was the non-adherence rate of LBP patients to hydrotherapy followed by the cost of hydrotherapy treatment. Fig. 2 View largeDownload slide Tornado diagram showing the 10 most influential input parameters for cost-effectiveness, The bar represents one-way sensitivity analysis evaluating the effect of changing each parameter on the overall incremental cost-effectiveness ratio (ICER). The central line represents the ICER of base case analysis (SGD 27 471). The bars indicate estimated ICER when changing the parameters to upper and lower values. LBP, low back pain; THR, total hip replacement; OA, osteoarthritis. Fig. 2 View largeDownload slide Tornado diagram showing the 10 most influential input parameters for cost-effectiveness, The bar represents one-way sensitivity analysis evaluating the effect of changing each parameter on the overall incremental cost-effectiveness ratio (ICER). The central line represents the ICER of base case analysis (SGD 27 471). The bars indicate estimated ICER when changing the parameters to upper and lower values. LBP, low back pain; THR, total hip replacement; OA, osteoarthritis. As shown in the cost-effectiveness acceptability curve (Fig. 3), the probabilistic sensitivity analysis detected SGD 26 320 per QALY as the value where the model was indifferent to hydrotherapy and land-based therapy in terms of cost-effectiveness. By increasing the willingness-to-pay value, the likelihood that hydrotherapy being a cost-effective treatment increased to almost 100% when the value was SGD 70 000 per QALY. Fig. 3 View largeDownload slide Cost-effectiveness acceptability curve showing probability of being cost-effective. The curves indicate the likelihood of hydrotherapy and land-based therapy being a cost-effective treatment over a range of willingness-to-pay threshold. At a willingness-to-pay threshold of SGD 70 000 per quality-adjusted life-years gained, hydrotherapy demonstrated a probability of almost 100% being more cost-effective than land-based therapy. QALY, quality-adjusted life-years. Fig. 3 View largeDownload slide Cost-effectiveness acceptability curve showing probability of being cost-effective. The curves indicate the likelihood of hydrotherapy and land-based therapy being a cost-effective treatment over a range of willingness-to-pay threshold. At a willingness-to-pay threshold of SGD 70 000 per quality-adjusted life-years gained, hydrotherapy demonstrated a probability of almost 100% being more cost-effective than land-based therapy. QALY, quality-adjusted life-years. Discussion Main findings of this study Our study demonstrated that hydrotherapy was a cost-effective rehabilitation treatment in patients with MSDs. Compared with land-based therapy, hydrotherapy was associated with an ICER of SGD 27 471 per QALY gained, which was considered cost-effective if we benchmarked the ICER against a willingness-to-pay threshold of SGD 70 000 per QALY. However, hydrotherapy did not achieve a favourable outcome in patients with OA. The cost-effectiveness of hydrotherapy was most sensitive to changes in the parameters related to LBP, the dominant users in our study. Six characteristics of LBP group including both clinical and economic factors are among the 10 most influential parameters. What is already known on the topic Chronic LBP, OA and RA are the top three MSDs causing the disability-adjusted life-years in Singapore.29 Total hip replacement and TKR, closely associated with OA and RA,30 have exerted great economic burden on patients and healthcare system.31,32 What this study adds Hydrotherapy that is beneficial in improving patients’ function and thus reducing the need for THR and TKR would have dual effect on both the disease and economic burden. Our model projected that, despite a variation of ICERs across the individual MSDs, hydrotherapy was a cost-effective treatment for MSDs in Singapore. This finding provides important insights to healthcare institutions which consider providing hydrotherapy services to their patients. To our knowledge, this study is the first modelling-based economic evaluation to assess the cost-effectiveness of hydrotherapy for a population with mixed MSDs. Unlike clinical interventions which have strict indications and contraindications to guide their use, rehabilitation generally caters to a spectrum of clinical conditions as a sequela of various diseases.33 As such, we chose to model a heterogeneous cohort consisted of patients with five different MSDs based on the real-world data instead of a simplified homogenous cohort. The subgroup analyses suggested that patients undergoing THR and TKR should be preferably considered for hydrotherapy after the procedures, while for patients with OA, hydrotherapy may not be economically as beneficial as land-based therapy. Although the relative ranking was informative to prioritize resource allocation in a specific jurisdiction, it may not serve as good evidence to exclude OA from target users of hydrotherapy given that cost-effectiveness is only one of the decision-making criteria by clinicians to choose amongst competing treatment alternatives. Limitations of this study Several limitations exist in our study that should be acknowledged. Our model adopted a 3-month time horizon to ensure a valid pooling of societal cost and QALYs of different MSDs. This technical arrangement presented two limitations. One is that the model captured only immediate effect on quality of life which may be unfair to certain conditions. Some conditions may require a longer modelling period to have a comprehensive comparison between hydrotherapy and land-based therapy.14 The other limitation associated with the short time horizon is the over-estimation of QALYs as clinical events such as death were not considered in the model. Data transferability may pose another limitation. The effectiveness data applied in the model were derived from studies conducted in other healthcare jurisdictions based on the assumption that similar utility gains could be achieved by our local hydrotherapy programmes. To ensure internal validity of our results, we sought expert opinion to verify that the utilities were applicable to local context. Lastly, the cost impact of hydrotherapy was not fully reflected in the model. Compared with the study by Cochrane et al.13 our model did not consider other treatment related costs such as medications and devices. Conclusions Our study demonstrated that hydrotherapy was a cost-effective rehabilitation treatment to improve the quality of life for patients with MSDs in Singapore. However, the cost-effectiveness of hydrotherapy was not observed in patients with OA. Funding This work was not supported by any grant or funding. References 1 The Burden of Musculoskeletal Diseases in the United States . Prevalence, Societal and Economic Cost (3rd Edition), the United States Bone and Joint Initiative, NFP (USBJI). http://www.boneandjointburden.org/. (25 September 2017, date last accessed). 2 Bevan S . Economic impact of musculoskeletal disorders (MSDs) on work in Europe . Best Pract Res Clin Rheumatol 2015 ; 29 : 356 – 73 . doi:10.1016/j.berh.2015.08.002 . Google Scholar CrossRef Search ADS PubMed 3 G. B. D. Disease Injury, I. P., Collaborators . Global, regional, and national incidence, prevalence, and years lived with disability for 328 diseases and injuries for 195 countries, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016 . Lancet 2017 ; 390 : 1211 – 59 . doi:10.1016/S0140-6736(17)32154-2 . CrossRef Search ADS PubMed 4 Hagen KB et al. . Exercise therapy for bone and muscle health: an overview of systematic reviews . BMC Med 2012 ; 10 : 167 . doi:10.1186/1741-7015-10-167 . Google Scholar CrossRef Search ADS PubMed 5 Baena-Beato PA et al. . Aquatic therapy improves pain, disability, quality of life, body composition and fitness in sedentary adults with chronic low back pain. A controlled clinical trial . Clin Rehabil 2014 ; 28 : 350 – 60 . doi:10.1177/0269215513504943 . Google Scholar CrossRef Search ADS PubMed 6 Bilberg A , Ahlmen M , Mannerkorpi K . Moderately intensive exercise in a temperate pool for patients with rheumatoid arthritis: a randomized controlled study . Rheumatology (Oxford, England) 2005 ; 44 : 502 – 8 . doi:10.1093/rheumatology/keh528 . Google Scholar CrossRef Search ADS PubMed 7 Foley A , Halbert J , Hewitt T et al. . Does hydrotherapy improve strength and physical function in patients with osteoarthritis—a randomised controlled trial comparing a gym based and a hydrotherapy based strengthening programme . Ann Rheum Dis 2003 ; 62 : 1162 – 7 . Google Scholar CrossRef Search ADS PubMed 8 Volpe D , Giantin MG , Maestri R et al. . Comparing the effects of hydrotherapy and land-based therapy on balance in patients with Parkinson’s disease: a randomized controlled pilot study . Clin Rehabil 2014 ; 28 : 1210 – 7 . doi:10.1177/0269215514536060 . Google Scholar CrossRef Search ADS PubMed 9 Dundar U , Solak O , Yigit I et al. . Clinical effectiveness of aquatic exercise to treat chronic low back pain: a randomized controlled trial . Spine 2009 ; 34 : 1436 – 40 . doi:10.1097/BRS.0b013e3181a79618 . Google Scholar CrossRef Search ADS PubMed 10 Silva LE et al. . Hydrotherapy versus conventional land-based exercise for the management of patients with osteoarthritis of the knee: a randomized clinical trial . Phys Ther 2008 ; 88 : 12 – 21 . doi:10.2522/ptj.20060040 . Google Scholar CrossRef Search ADS PubMed 11 Eversden L , Maggs F , Nightingale P et al. . A pragmatic randomised controlled trial of hydrotherapy and land exercises on overall well being and quality of life in rheumatoid arthritis . BMC Musculoskelet Disord 2007 ; 8 : 23 . doi:10.1186/1471-2474-8-23 . Google Scholar CrossRef Search ADS PubMed 12 Rahmann AE , Brauer SG , Nitz JC . A specific inpatient aquatic physiotherapy program improves strength after total hip or knee replacement surgery: a randomized controlled trial . Arch Phys Med Rehabil 2009 ; 90 : 745 – 55 . doi:10.1016/j.apmr.2008.12.011 . Google Scholar CrossRef Search ADS PubMed 13 Cochrane T , Davey RC , Matthes Edwards SM . Randomised controlled trial of the cost-effectiveness of water-based therapy for lower limb osteoarthritis . Health Technol Assess 2005 ; 9 : iii – iv . ix–xi, 1–114. Google Scholar CrossRef Search ADS PubMed 14 Patrick DL et al. . Economic evaluation of aquatic exercise for persons with osteoarthritis . Med care 2001 ; 39 : 413 – 24 . Google Scholar CrossRef Search ADS PubMed 15 Baena-Beato PA , Arroyo-Morales M , Delgado-Fernandez M et al. . Effects of different frequencies (2-3 days/week) of aquatic therapy program in adults with chronic low back pain. A non-randomized comparison trial . Pain Med 2013 ; 14 : 145 – 58 . doi:10.1111/pme.12002 . Google Scholar CrossRef Search ADS PubMed 16 Wang TJ et al. . Comparing the efficacy of aquatic exercises and land-based exercises for patients with knee osteoarthritis . J Clin Nurs 2011 ; 20 : 2609 – 22 . doi:10.1111/j.1365-2702.2010.03675.x . Google Scholar CrossRef Search ADS PubMed 17 Lim JY , Tchai E , Jang SN . Effectiveness of aquatic exercise for obese patients with knee osteoarthritis: a randomized controlled trial . PM R 2010 ; 2 : 723 – 731 . quiz 793. doi:10.1016/j.pmrj.2010.04.004 . Google Scholar CrossRef Search ADS PubMed 18 Hinman RS , Heywood SE , Day AR . Aquatic physical therapy for hip and knee osteoarthritis: results of a single-blind randomized controlled trial . Phys Ther 2007 ; 87 : 32 – 43 . doi:10.2522/ptj.20060006 . Google Scholar CrossRef Search ADS PubMed 19 Jack K , McLean SM , Moffett JK et al. . Barriers to treatment adherence in physiotherapy outpatient clinics: a systematic review . Man Ther 2010 ; 15 : 220 – 8 . doi:10.1016/j.math.2009.12.004 . Google Scholar CrossRef Search ADS PubMed 20 Sachs JD . Macroeconomics and Health: Investing in Health for Economic Development. Report of the Commission on Macroeconomics and Health . Geneva, Switzerland : World Health Organisation , 2011 . http://whqlibdoc.who.int/publications/2001/924154550×.pdf. (16 January 2018, date last accessed). 21 Fares and payment methods 2015 . Land Transport Authority, Singapore. 22 Singapore Land Transport : Statistics in Brief 2015. Land Transport Authority, Singapore. 23 Labour market statistical information : Unemployment 2015. Ministry of Manpower, Singapore. 24 Koh ET , Tan JW , Thong BY et al. . Major trends in the manifestations and treatment of rheumatoid arthritis in a multiethnic cohort in Singapore . Rheumatol Int 2013 ; 33 : 1693 – 1703 . doi:10.1007/s00296-012-2602-2 . Google Scholar CrossRef Search ADS PubMed 25 Harmer AR , Naylor JM , Crosbie J et al. . Land-based versus water-based rehabilitation following total knee replacement: a randomized, single-blind trial . Arthritis Rheum 2009 ; 61 : 184 – 91 . doi:10.1002/art.24420 . Google Scholar CrossRef Search ADS PubMed 26 Chuang LH , Whitehead SJ . Mapping for economic evaluation . Br Med Bull 2012 ; 101 : 1 – 15 . doi:10.1093/bmb/ldr049 . Google Scholar CrossRef Search ADS PubMed 27 Longworth L , Rowen D . NICE DSU Technical Support Document 10: The Use of Mapping Methods to Estimate Health State Utility Values NICE Decision Support Unit Technical Support Documents ( 2011 ). 28 Drummond MF , Sculpher MJ , Claxton K et al. . Methods for the Economic Evaluation of Health Care Programmes , 3rd edn . Canada : Oxford University Press , 2005 . 29 Singapore Burden of Disease Study . Epidemiology & Disease Control Division . Singapore : Ministry of Health , 2010 . 30 Liao CY , Chan HT , Chao E et al. . Comparison of total hip and knee joint replacement in patients with rheumatoid arthritis and osteoarthritis: a nationwide, population-based study . Singapore Med J 2015 ; 56 : 58 – 64 . Google Scholar CrossRef Search ADS PubMed 31 Ministry of Health . Total Hospital Bills by Condition or Procedure. Hip Replacement Surgery . Singapore : Ministry of Health , 2015 . www.moh.gov.sg. (30 January 2016, date last accessed). 32 Ministry of Health . Total Hospital Bills by Condition or Procedure. Knee Replacement Surgery . Singapore : Ministry of Health , 2015 . www.moh.gov.sg. (30 January 2016, date last accessed). 33 Wade DT . Describing rehabilitation interventions . Clin Rehabil 2005 ; 19 : 811 – 8 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of Faculty of Public Health. All rights reserved. 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Cost-effectiveness of hydrotherapy versus land-based therapy in patients with musculoskeletal disorders in Singapore

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Abstract

Abstract Background The study evaluated the cost-effectiveness of hydrotherapy versus land-based therapy in patients with musculoskeletal disorders (MSDs) in Singapore. Methods A decision-analytic model was constructed to compare the cost-effectiveness of hydrotherapy to land-based therapy over 3 months from societal perspective. Target population comprised patients with low back pain (LBP), osteoarthritis (OA), rheumatoid arthritis (RA), total hip replacement (THR) and total knee replacement (TKR). Subgroup analyses were carried out to determine the cost-effectiveness of hydrotherapy in individual MSDs. Relative treatment effects were obtained through a systematic review of published data. Results Compared to land-based therapy, hydrotherapy was associated with an incremental cost-effectiveness ratio (ICER) of SGD 27 471 per quality-adjusted life-year (QALY) gained, which was below the willingness-to-pay threshold of SGD 70 000 per QALY (one gross domestic product per capita in Singapore in 2015). For the respective MSDs, hydrotherapy were dominant (more effective and less costly) in THR and TKR, cost-effective for LBP and RA, and not cost-effective for OA. Treatment adherence and cost of hydrotherapy were key drivers to the ICER values. Conclusions Hydrotherapy was a cost-effective rehabilitation compared to land-based therapy for a population with MSDs in Singapore. However, the benefit of hydrotherapy was not observed in patients with OA. cost-effective analysis, economic model, hydrotherapy, low back pain, musculoskeletal diseases Introduction Musculoskeletal disorders (MSDs) refer to a variety of conditions affecting bones, joints and muscles. The burden of MSDs is significant in terms of treatment, the impact on quality of life and productivity. The annual cost for treatment and lost wages associated with MSDs in the United States (US) was USD 213 billion,1 while across the European countries, MSDs accounted for 53% of all work-related diseases incurring €240 billion.2 According to the Global Burden of Disease Study 2016, low back pain (LBP) was the leading cause of disability especially in developed countries.3 As such, effective treatment strategies are crucial to reduce MSD-related financial burden for patients as well as healthcare system. Although MSDs are generally nonfatal, the debilitating nature can lead to deterioration of patients’ function and quality of life. Rehabilitation plays an important role in the management of patients with MSDs. Land-based physiotherapy ranging from patient education to exercise has been shown to be effective in reducing pain and improving patients’ function.4 There has been a growing body of evidence to support the use of hydrotherapy in chronic musculoskeletal conditions.5–8 Compared to land-based physiotherapy, hydrotherapy utilizes the unique properties of water to reinforce rehabilitative efforts by enhancing relaxation, decreasing pain, improving strength and helping with balance. Both hydrotherapy and land-based therapy have shown benefits in the treatment of MSDs including chronic LBP, osteoarthritis (OA) and rheumatoid arthritis (RA).9–11 Besides the standard benefits of land-based exercise such as increased muscle strength, improved aerobic and cardiovascular capacity, the buoyancy of water may reduce the risk of muscle or joint injury associated with exercise. Because of this advantage, hydrotherapy is suggested as an initial treatment option for patients requiring early rehabilitation such as post-surgery.12 Given the relatively high operating cost for an in-house pool, hydrotherapy is not adopted as a routine clinical practice in most healthcare facilities. Apart from a paucity of cost-effectiveness data on hydrotherapy compared to land-based therapy, published cost-effectiveness findings have been inconsistent. Hydrotherapy was reported as a cost-effective rehabilitation when compared to usual care in patients with OA in the United Kingdom (UK), with an incremental cost-effectiveness ratios (ICERs) ranging from £3838 to £5951 per quality-adjusted life-year (QALY), well below the UK National Institute for Health and Care Excellence (NICE) threshold of £20 000 per QALY gained.13 On the other hand, hydrotherapy did not achieve a better outcome and reduced cost compared with usual care in the USA.14 Given that the differing conclusions could be due to different healthcare settings and costs of treatment, we evaluated the cost-effectiveness of hydrotherapy versus land-based therapy in patients with MSDs comprising LBP, OA, RA, total hip replacement (THR) and total knee replacement (TKR) in Singapore. We also identified which particular musculoskeletal conditions would benefit most from hydrotherapy. Methods Model overview A decision-analytic model in the form of a decision tree was developed to estimate the societal cost and QALY of a cohort of patients with MSDs receiving hydrotherapy or land-based therapy (Fig. 1). The target population comprised of patients with LBP, OA, RA, THR and TKR; and the distribution of these conditions was estimated from a real-world patients (n = 23 440) seeking rehabilitation in a public hospital in Singapore in 2014. The relative distributions of the different types of MSDs were: LBP (93.49%), OA (3.0%), RA (0.73%), THR (0.59%) and TKR (2.18%). Both THR and TKR received rehabilitation services in an inpatient setting while treatment for LBP, OA and RA were provided on an outpatient basis. These proportions representing the disease profile of the target cohort were inputted into the model to reflect real-world setting. In addition, the model was structured to reflect the utilization pattern of hydrotherapy and land-based therapy in Singapore. Patients with THR and TKR were modelled as post-operative rehabilitation in inpatient setting while patients with LBP, OR and RA were treated in outpatient setting. Fig. 1 View largeDownload slide Schematic representation of model structure. Fig. 1 View largeDownload slide Schematic representation of model structure. The model duration was set as 3 months considering the disease heterogeneity of the target cohort and duration of most rehabilitation programmes ranged from 4 to 12 weeks.5,6,9,11,15–18 During this time horizon, the model was expected to capture the clinical benefit of the treatment while maintaining homogeneity of the outputs, which are cost and QALYs across the different MSDs. This ensures the validity of the final composite outcomes from a combination of condition-specific outputs for the entire cohort. A longer time horizon would require more assumptions on the clinical outcomes for individual MSDs which in turn may introduce greater uncertainties and probability of biases in the model. Treatment benefits were reflected in terms of an improvement in quality of life and achievement of treatment goal as informed by literature. As rehabilitation therapy is generally safe and in view of the relatively short modelling period,12 the model did not include adverse events. Premature termination of treatment has been reported for both hydrotherapy and land-based therapy and this non-adherence has implication on the cost-effectiveness of the treatments.19 Therefore, we modelled the impact of non-adherence for patients with LBP,5,15 OA13,14 and RA6,11 and assumed patients with THR and TKR to be fully compliant given the inpatient setting. Total societal cost and QALYs for hydrotherapy and land-based therapy were estimated by the model. Discounting was not applied considering the relatively short model duration. An ICER represents the incremental cost incurred for each additional QALY gained by hydrotherapy as compared to land-based therapy. The cost-effectiveness threshold or willingness-to-pay was set as SGD 70 000 (one gross domestic product per capita in Singapore in 2015) following the World Health Organization’s recommendation.20 An ICER below this threshold indicates that the treatment is cost-effective compare to the baseline comparator in Singapore. The model was developed and analysed using TreeAge Pro Suite software 2016 (Williamstown, MA, USA). Cost We adopted a societal perspective by including both direct and indirect cost involved in the provision of rehabilitative treatment in Singapore. The cost in our model represented the societal economic burden in providing the two rehabilitation strategies in Singapore. Direct medical cost included cost of treatment, hospitalization and therapist visits, which was estimated by a micro-costing approach by multiplying unit price with the amount of resource consumed. We obtained healthcare resource use and cost data from hospital database (Table 1). Non-medical cost included transportation fees during treatment period that were based on data from the Land Transport Authority in Singapore.21,22 Given that the cohort comprised of a substantial proportion of outpatients (LBP, OA and RA), we also incorporated indirect cost as measured by absenteeism for seeking rehabilitation. The associated productivity loss was the product of national mean salary and duration of absenteeism,23,24 following the human capital approach. Costs were calculated in Singapore dollars (1 Singapore dollar = 0.72 US dollars as of November 2016). Table 1 Cost estimates based on resource consumption for hydrotherapy and land-based therapy Cost components Land-based therapy Hydrotherapy Source Point estimate Range Distribution Point estimate Range Distribution Direct cost  Rehabilitation cost   Cost per session (SGD)    Total hip replacement 99 NA NA 110 NA NA Hospital    Total knee replacement 99 NA NA 110 NA NA Hospital    Low back pain 60 NA NA 78 NA NA Hospital    Osteoarthritis 60 NA NA 78 NA NA Hospital    Rheumatoid arthritis 60 NA NA 78 NA NA Hospital   Treatment frequency (weekly sessions)    Total hip replacement 5 NA NA 5 NA NA Hospital    Total knee replacement 5 NA NA 5 NA NA Hospital    Low back pain 1.5 (1–2) Triangular 1.5 (1–2) Triangular Hospital    Osteoarthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital    Rheumatoid arthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital   Treatment duration (week)    Total hip replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Total knee replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Low back pain 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Osteoarthritis 4 NA NA 4 NA NA Hospital    Rheumatoid arthritis 4 NA NA 4 NA NA Hospital   Hospital stay (day)    Total hip replacement 35 (14–55) Triangular    Total knee replacement 22 (5–28) Triangular   Reduction in hospital stay 0 0 NA 1 (0–2) Triangular (12)   Daily cost of hospitalization (SGD) 402 NA NA 402 NA NA Hospital  Post-discharge rehabilitation   Number of sessions    Total hip replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital    Total knee replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital   Cost per session (SGD) 110 NA NA 80 NA NA Hospital  Transport cost (SGD) 8.3 (7.8–8.7) Triangular 8.3 (7.8–8.7) Triangular (21) Indirect cost  Percentage of working patients (%)   Low back pain 56 55–57 Beta 56 55–57 Beta Hospital   Osteoarthritis 51 43–60 Beta 51 43–60 Beta Hospital, (23)   Rheumatoid arthritis 44 41–47 Beta 43.5 41–47 Beta (24)  Disease-specific absenteeism (day)   Osteoarthritis 28 NA NA 28 NA NA Hospital   Rheumatoid arthritis 28 NA NA 28 NA NA Hospital   Low back pain 25 NA NA 25 NA NA Hospital  Daily cost of productivity loss (SGD) 124 NA NA 124 NA NA (23) Cost components Land-based therapy Hydrotherapy Source Point estimate Range Distribution Point estimate Range Distribution Direct cost  Rehabilitation cost   Cost per session (SGD)    Total hip replacement 99 NA NA 110 NA NA Hospital    Total knee replacement 99 NA NA 110 NA NA Hospital    Low back pain 60 NA NA 78 NA NA Hospital    Osteoarthritis 60 NA NA 78 NA NA Hospital    Rheumatoid arthritis 60 NA NA 78 NA NA Hospital   Treatment frequency (weekly sessions)    Total hip replacement 5 NA NA 5 NA NA Hospital    Total knee replacement 5 NA NA 5 NA NA Hospital    Low back pain 1.5 (1–2) Triangular 1.5 (1–2) Triangular Hospital    Osteoarthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital    Rheumatoid arthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital   Treatment duration (week)    Total hip replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Total knee replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Low back pain 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Osteoarthritis 4 NA NA 4 NA NA Hospital    Rheumatoid arthritis 4 NA NA 4 NA NA Hospital   Hospital stay (day)    Total hip replacement 35 (14–55) Triangular    Total knee replacement 22 (5–28) Triangular   Reduction in hospital stay 0 0 NA 1 (0–2) Triangular (12)   Daily cost of hospitalization (SGD) 402 NA NA 402 NA NA Hospital  Post-discharge rehabilitation   Number of sessions    Total hip replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital    Total knee replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital   Cost per session (SGD) 110 NA NA 80 NA NA Hospital  Transport cost (SGD) 8.3 (7.8–8.7) Triangular 8.3 (7.8–8.7) Triangular (21) Indirect cost  Percentage of working patients (%)   Low back pain 56 55–57 Beta 56 55–57 Beta Hospital   Osteoarthritis 51 43–60 Beta 51 43–60 Beta Hospital, (23)   Rheumatoid arthritis 44 41–47 Beta 43.5 41–47 Beta (24)  Disease-specific absenteeism (day)   Osteoarthritis 28 NA NA 28 NA NA Hospital   Rheumatoid arthritis 28 NA NA 28 NA NA Hospital   Low back pain 25 NA NA 25 NA NA Hospital  Daily cost of productivity loss (SGD) 124 NA NA 124 NA NA (23) NA, not applicable. Table 1 Cost estimates based on resource consumption for hydrotherapy and land-based therapy Cost components Land-based therapy Hydrotherapy Source Point estimate Range Distribution Point estimate Range Distribution Direct cost  Rehabilitation cost   Cost per session (SGD)    Total hip replacement 99 NA NA 110 NA NA Hospital    Total knee replacement 99 NA NA 110 NA NA Hospital    Low back pain 60 NA NA 78 NA NA Hospital    Osteoarthritis 60 NA NA 78 NA NA Hospital    Rheumatoid arthritis 60 NA NA 78 NA NA Hospital   Treatment frequency (weekly sessions)    Total hip replacement 5 NA NA 5 NA NA Hospital    Total knee replacement 5 NA NA 5 NA NA Hospital    Low back pain 1.5 (1–2) Triangular 1.5 (1–2) Triangular Hospital    Osteoarthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital    Rheumatoid arthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital   Treatment duration (week)    Total hip replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Total knee replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Low back pain 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Osteoarthritis 4 NA NA 4 NA NA Hospital    Rheumatoid arthritis 4 NA NA 4 NA NA Hospital   Hospital stay (day)    Total hip replacement 35 (14–55) Triangular    Total knee replacement 22 (5–28) Triangular   Reduction in hospital stay 0 0 NA 1 (0–2) Triangular (12)   Daily cost of hospitalization (SGD) 402 NA NA 402 NA NA Hospital  Post-discharge rehabilitation   Number of sessions    Total hip replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital    Total knee replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital   Cost per session (SGD) 110 NA NA 80 NA NA Hospital  Transport cost (SGD) 8.3 (7.8–8.7) Triangular 8.3 (7.8–8.7) Triangular (21) Indirect cost  Percentage of working patients (%)   Low back pain 56 55–57 Beta 56 55–57 Beta Hospital   Osteoarthritis 51 43–60 Beta 51 43–60 Beta Hospital, (23)   Rheumatoid arthritis 44 41–47 Beta 43.5 41–47 Beta (24)  Disease-specific absenteeism (day)   Osteoarthritis 28 NA NA 28 NA NA Hospital   Rheumatoid arthritis 28 NA NA 28 NA NA Hospital   Low back pain 25 NA NA 25 NA NA Hospital  Daily cost of productivity loss (SGD) 124 NA NA 124 NA NA (23) Cost components Land-based therapy Hydrotherapy Source Point estimate Range Distribution Point estimate Range Distribution Direct cost  Rehabilitation cost   Cost per session (SGD)    Total hip replacement 99 NA NA 110 NA NA Hospital    Total knee replacement 99 NA NA 110 NA NA Hospital    Low back pain 60 NA NA 78 NA NA Hospital    Osteoarthritis 60 NA NA 78 NA NA Hospital    Rheumatoid arthritis 60 NA NA 78 NA NA Hospital   Treatment frequency (weekly sessions)    Total hip replacement 5 NA NA 5 NA NA Hospital    Total knee replacement 5 NA NA 5 NA NA Hospital    Low back pain 1.5 (1–2) Triangular 1.5 (1–2) Triangular Hospital    Osteoarthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital    Rheumatoid arthritis 2.5 (2–3) Triangular 2.5 (2–3) Triangular Hospital   Treatment duration (week)    Total hip replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Total knee replacement 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Low back pain 3.5 (3–4) Triangular 3.5 (3–4) Triangular Hospital    Osteoarthritis 4 NA NA 4 NA NA Hospital    Rheumatoid arthritis 4 NA NA 4 NA NA Hospital   Hospital stay (day)    Total hip replacement 35 (14–55) Triangular    Total knee replacement 22 (5–28) Triangular   Reduction in hospital stay 0 0 NA 1 (0–2) Triangular (12)   Daily cost of hospitalization (SGD) 402 NA NA 402 NA NA Hospital  Post-discharge rehabilitation   Number of sessions    Total hip replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital    Total knee replacement 3.5 (2–5) Triangular 3.5 (2–5) Triangular Hospital   Cost per session (SGD) 110 NA NA 80 NA NA Hospital  Transport cost (SGD) 8.3 (7.8–8.7) Triangular 8.3 (7.8–8.7) Triangular (21) Indirect cost  Percentage of working patients (%)   Low back pain 56 55–57 Beta 56 55–57 Beta Hospital   Osteoarthritis 51 43–60 Beta 51 43–60 Beta Hospital, (23)   Rheumatoid arthritis 44 41–47 Beta 43.5 41–47 Beta (24)  Disease-specific absenteeism (day)   Osteoarthritis 28 NA NA 28 NA NA Hospital   Rheumatoid arthritis 28 NA NA 28 NA NA Hospital   Low back pain 25 NA NA 25 NA NA Hospital  Daily cost of productivity loss (SGD) 124 NA NA 124 NA NA (23) NA, not applicable. Health outcomes The outcome of interest was QALY gained that incorporates utility and quantity of life lived. Utilities in our model were represented by the EQ-5D scores, which measure preferences for health state ranging from 0 (death) to 1 (perfect health). The EQ-5D scores were derived from a systematic literature search using PubMed up to September 2015 for studies comparing hydrotherapy versus land-based therapy in patients with LBP,5,15 OA,13,14 RA,6,11 THR12 and TKR.12,25 Where EQ-5D data were not reported, we transformed the original scores measured by other quality of life instruments into EQ-5D values following the validated mapping algorithm.26 Utility data based on generic quality of life instrument such as EQ-5D are ideal and preferred to estimate the QALY impact. However, the UK National Institute for Health and Clinical Excellence (NICE) has recognized that mapping using an algorithm to predict health state utility values based on other measures of health are a valid approach to derive utility values when EQ-5D data are not available.27 For a fair comparison, our model assumed that patients receiving hydrotherapy and land-based therapy had same pre-rehabilitation utility which was a pooled mean of EQ-5D for individual conditions (Table 2). The differential effects on the quality of life by hydrotherapy and land-based therapy were calculated as a utility gain after a full course of exercise programme. In the situation of non-adherence, patients were assumed to drop out halfway and as such the utility gain was assumed to be null for the entire modelling period. Table 2 Parameters representing clinical effectiveness for hydrotherapy and land-based therapy Conditions Land-based therapy Hydrotherapy Source Point estimate Range/95% CI Distribution Point estimate Range/95% CI Distribution Pre-rehabilitation utility  Total hip replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12)  Total knee replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12, 25)  Low back pain 0.68 (0.64–0.71) Normal 0.68 (0.64–0.71) Normal (5, 15)  Osteoarthritis 0.68 (0.64–0.72) Normal 0.68 (0.64–0.72) Normal (13, 14)  Rheumatoid arthritis 0.66 (0.60–0.72) Normal 0.66 (0.60–0.72) Normal (6, 11) Post-rehabilitation utility gain  Total hip replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12)  Total knee replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12, 25)  Low back pain 0 NA NA 0.128 (0.121–0.135) Normal (5, 15)  Osteoarthritis 0 NA NA 0.017 (0–0.034) Normal (13, 14)  Rheumatoid arthritis 0.003 (0.001–0.100) LogNormal 0.091 (0.074–0.108) Normal (6, 11) Non-adherence rate (%)  Low back pain 0 NA Beta 11.1 (4.9–20.7) Beta (5, 15)  Osteoarthritis 6.9 (4.9–9.3) Beta 7.7 (5.6–10.3) Beta (13, 14)  Rheumatoid arthritis 7.3 (2.4–16.1) Beta 14.7 (7.6–24.7) Beta (6, 11) Conditions Land-based therapy Hydrotherapy Source Point estimate Range/95% CI Distribution Point estimate Range/95% CI Distribution Pre-rehabilitation utility  Total hip replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12)  Total knee replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12, 25)  Low back pain 0.68 (0.64–0.71) Normal 0.68 (0.64–0.71) Normal (5, 15)  Osteoarthritis 0.68 (0.64–0.72) Normal 0.68 (0.64–0.72) Normal (13, 14)  Rheumatoid arthritis 0.66 (0.60–0.72) Normal 0.66 (0.60–0.72) Normal (6, 11) Post-rehabilitation utility gain  Total hip replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12)  Total knee replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12, 25)  Low back pain 0 NA NA 0.128 (0.121–0.135) Normal (5, 15)  Osteoarthritis 0 NA NA 0.017 (0–0.034) Normal (13, 14)  Rheumatoid arthritis 0.003 (0.001–0.100) LogNormal 0.091 (0.074–0.108) Normal (6, 11) Non-adherence rate (%)  Low back pain 0 NA Beta 11.1 (4.9–20.7) Beta (5, 15)  Osteoarthritis 6.9 (4.9–9.3) Beta 7.7 (5.6–10.3) Beta (13, 14)  Rheumatoid arthritis 7.3 (2.4–16.1) Beta 14.7 (7.6–24.7) Beta (6, 11) NA: not applicable. Table 2 Parameters representing clinical effectiveness for hydrotherapy and land-based therapy Conditions Land-based therapy Hydrotherapy Source Point estimate Range/95% CI Distribution Point estimate Range/95% CI Distribution Pre-rehabilitation utility  Total hip replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12)  Total knee replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12, 25)  Low back pain 0.68 (0.64–0.71) Normal 0.68 (0.64–0.71) Normal (5, 15)  Osteoarthritis 0.68 (0.64–0.72) Normal 0.68 (0.64–0.72) Normal (13, 14)  Rheumatoid arthritis 0.66 (0.60–0.72) Normal 0.66 (0.60–0.72) Normal (6, 11) Post-rehabilitation utility gain  Total hip replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12)  Total knee replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12, 25)  Low back pain 0 NA NA 0.128 (0.121–0.135) Normal (5, 15)  Osteoarthritis 0 NA NA 0.017 (0–0.034) Normal (13, 14)  Rheumatoid arthritis 0.003 (0.001–0.100) LogNormal 0.091 (0.074–0.108) Normal (6, 11) Non-adherence rate (%)  Low back pain 0 NA Beta 11.1 (4.9–20.7) Beta (5, 15)  Osteoarthritis 6.9 (4.9–9.3) Beta 7.7 (5.6–10.3) Beta (13, 14)  Rheumatoid arthritis 7.3 (2.4–16.1) Beta 14.7 (7.6–24.7) Beta (6, 11) Conditions Land-based therapy Hydrotherapy Source Point estimate Range/95% CI Distribution Point estimate Range/95% CI Distribution Pre-rehabilitation utility  Total hip replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12)  Total knee replacement 0.71 (0.70–0.713) Normal 0.71 (0.70–0.713) Normal (12, 25)  Low back pain 0.68 (0.64–0.71) Normal 0.68 (0.64–0.71) Normal (5, 15)  Osteoarthritis 0.68 (0.64–0.72) Normal 0.68 (0.64–0.72) Normal (13, 14)  Rheumatoid arthritis 0.66 (0.60–0.72) Normal 0.66 (0.60–0.72) Normal (6, 11) Post-rehabilitation utility gain  Total hip replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12)  Total knee replacement 0.099 (0.096–0.102) Normal 0.111 (0.108–0.114) Normal (12, 25)  Low back pain 0 NA NA 0.128 (0.121–0.135) Normal (5, 15)  Osteoarthritis 0 NA NA 0.017 (0–0.034) Normal (13, 14)  Rheumatoid arthritis 0.003 (0.001–0.100) LogNormal 0.091 (0.074–0.108) Normal (6, 11) Non-adherence rate (%)  Low back pain 0 NA Beta 11.1 (4.9–20.7) Beta (5, 15)  Osteoarthritis 6.9 (4.9–9.3) Beta 7.7 (5.6–10.3) Beta (13, 14)  Rheumatoid arthritis 7.3 (2.4–16.1) Beta 14.7 (7.6–24.7) Beta (6, 11) NA: not applicable. Subgroup analyses Subgroup analysis was conducted for individual musculoskeletal conditions to provide comprehensive insights into the value of hydrotherapy as compared to land-based therapy. Sensitivity analyses Deterministic sensitivity analyses where key model inputs were varied across their plausible ranges were carried out to identify influential parameters on cost-effectiveness. In deterministic sensitivity analysis, the value of each input parameter was varied one at a time to evaluate how this variation affects the results. The results were presented as a tornado diagram showing the relative importance of each parameter. Probabilistic sensitivity analysis evaluating the robustness of modelling conclusion was also conducted. The probabilistic sensitivity analysis takes into account the uncertainty of all model input parameters simultaneously and describes the implications of that uncertainty on cost-effectiveness results.28 The results were presented as a cost-effectiveness acceptability curve that showed the probability of hydrotherapy being a cost-effective treatment relative to land-based therapy at various willingness-to-pay thresholds. Results For the defined target cohort, the model projected that hydrotherapy incurred an additional cost of SGD 419 and yielded an additional 0.015 QALY, producing an ICER of SGD 27 471 per QALY gained compared to land-based therapy. The ICER value was well below the pre-defined threshold of SGD 70 000 per QALY for cost-effectiveness. The subgroup analysis demonstrated that the cost-effectiveness of hydrotherapy was heterogeneous across the five MSD conditions. Hydrotherapy was associated with a QALY gained of 0.002, and cost saving of SGD 107 for THR and SGD 106 for TKR, respectively. Hydrotherapy was cost-effective for LBP and RA with an ICER of SGD 30 250 and SGD 40 482 per QALY. However, it was not cost-effective for OA with an ICER of SGD 110 000 per QALY which was above one GDP per capita in Singapore in 2015 (Table 3). Table 3 Cost-effectiveness results Conditions Land-based therapy Hydrotherapy ICER (SGD per QALY gained) Cost (SGD) QALY gained Cost (SGD) QALY gained Total hip replacement 16 532 0.177 16 425 0.179 Dominanta Total knee replacement 11 373 0.177 11 267 0.179 Dominanta Low back pain 2116 0.156 2646 0.174 30 250 Rheumatoid arthritis 2469 0.152 2832 0.161 40 482 Osteoarthritis 2766 0.157 2966 0.159 110 000 Entire cohort 2642 0.157 3096 0.173 27 471 Conditions Land-based therapy Hydrotherapy ICER (SGD per QALY gained) Cost (SGD) QALY gained Cost (SGD) QALY gained Total hip replacement 16 532 0.177 16 425 0.179 Dominanta Total knee replacement 11 373 0.177 11 267 0.179 Dominanta Low back pain 2116 0.156 2646 0.174 30 250 Rheumatoid arthritis 2469 0.152 2832 0.161 40 482 Osteoarthritis 2766 0.157 2966 0.159 110 000 Entire cohort 2642 0.157 3096 0.173 27 471 aHydrotherapy dominated land-based therapy with more QALYs and less costly. QALY, quality-adjusted life-years; ICER, incremental cost-effectiveness ratio. Table 3 Cost-effectiveness results Conditions Land-based therapy Hydrotherapy ICER (SGD per QALY gained) Cost (SGD) QALY gained Cost (SGD) QALY gained Total hip replacement 16 532 0.177 16 425 0.179 Dominanta Total knee replacement 11 373 0.177 11 267 0.179 Dominanta Low back pain 2116 0.156 2646 0.174 30 250 Rheumatoid arthritis 2469 0.152 2832 0.161 40 482 Osteoarthritis 2766 0.157 2966 0.159 110 000 Entire cohort 2642 0.157 3096 0.173 27 471 Conditions Land-based therapy Hydrotherapy ICER (SGD per QALY gained) Cost (SGD) QALY gained Cost (SGD) QALY gained Total hip replacement 16 532 0.177 16 425 0.179 Dominanta Total knee replacement 11 373 0.177 11 267 0.179 Dominanta Low back pain 2116 0.156 2646 0.174 30 250 Rheumatoid arthritis 2469 0.152 2832 0.161 40 482 Osteoarthritis 2766 0.157 2966 0.159 110 000 Entire cohort 2642 0.157 3096 0.173 27 471 aHydrotherapy dominated land-based therapy with more QALYs and less costly. QALY, quality-adjusted life-years; ICER, incremental cost-effectiveness ratio. Based on the deterministic sensitivity analysis, none of the input parameters overturned the result that hydrotherapy was a cost-effective option, even though some parameters changed ICERs substantially. Among the 10 most influential parameters, 6 variables were related to LBP group (Fig. 2). This was within expectation because the majority (93.49%) of the target cohort was LBP patients. The most significant parameter was the non-adherence rate of LBP patients to hydrotherapy followed by the cost of hydrotherapy treatment. Fig. 2 View largeDownload slide Tornado diagram showing the 10 most influential input parameters for cost-effectiveness, The bar represents one-way sensitivity analysis evaluating the effect of changing each parameter on the overall incremental cost-effectiveness ratio (ICER). The central line represents the ICER of base case analysis (SGD 27 471). The bars indicate estimated ICER when changing the parameters to upper and lower values. LBP, low back pain; THR, total hip replacement; OA, osteoarthritis. Fig. 2 View largeDownload slide Tornado diagram showing the 10 most influential input parameters for cost-effectiveness, The bar represents one-way sensitivity analysis evaluating the effect of changing each parameter on the overall incremental cost-effectiveness ratio (ICER). The central line represents the ICER of base case analysis (SGD 27 471). The bars indicate estimated ICER when changing the parameters to upper and lower values. LBP, low back pain; THR, total hip replacement; OA, osteoarthritis. As shown in the cost-effectiveness acceptability curve (Fig. 3), the probabilistic sensitivity analysis detected SGD 26 320 per QALY as the value where the model was indifferent to hydrotherapy and land-based therapy in terms of cost-effectiveness. By increasing the willingness-to-pay value, the likelihood that hydrotherapy being a cost-effective treatment increased to almost 100% when the value was SGD 70 000 per QALY. Fig. 3 View largeDownload slide Cost-effectiveness acceptability curve showing probability of being cost-effective. The curves indicate the likelihood of hydrotherapy and land-based therapy being a cost-effective treatment over a range of willingness-to-pay threshold. At a willingness-to-pay threshold of SGD 70 000 per quality-adjusted life-years gained, hydrotherapy demonstrated a probability of almost 100% being more cost-effective than land-based therapy. QALY, quality-adjusted life-years. Fig. 3 View largeDownload slide Cost-effectiveness acceptability curve showing probability of being cost-effective. The curves indicate the likelihood of hydrotherapy and land-based therapy being a cost-effective treatment over a range of willingness-to-pay threshold. At a willingness-to-pay threshold of SGD 70 000 per quality-adjusted life-years gained, hydrotherapy demonstrated a probability of almost 100% being more cost-effective than land-based therapy. QALY, quality-adjusted life-years. Discussion Main findings of this study Our study demonstrated that hydrotherapy was a cost-effective rehabilitation treatment in patients with MSDs. Compared with land-based therapy, hydrotherapy was associated with an ICER of SGD 27 471 per QALY gained, which was considered cost-effective if we benchmarked the ICER against a willingness-to-pay threshold of SGD 70 000 per QALY. However, hydrotherapy did not achieve a favourable outcome in patients with OA. The cost-effectiveness of hydrotherapy was most sensitive to changes in the parameters related to LBP, the dominant users in our study. Six characteristics of LBP group including both clinical and economic factors are among the 10 most influential parameters. What is already known on the topic Chronic LBP, OA and RA are the top three MSDs causing the disability-adjusted life-years in Singapore.29 Total hip replacement and TKR, closely associated with OA and RA,30 have exerted great economic burden on patients and healthcare system.31,32 What this study adds Hydrotherapy that is beneficial in improving patients’ function and thus reducing the need for THR and TKR would have dual effect on both the disease and economic burden. Our model projected that, despite a variation of ICERs across the individual MSDs, hydrotherapy was a cost-effective treatment for MSDs in Singapore. This finding provides important insights to healthcare institutions which consider providing hydrotherapy services to their patients. To our knowledge, this study is the first modelling-based economic evaluation to assess the cost-effectiveness of hydrotherapy for a population with mixed MSDs. Unlike clinical interventions which have strict indications and contraindications to guide their use, rehabilitation generally caters to a spectrum of clinical conditions as a sequela of various diseases.33 As such, we chose to model a heterogeneous cohort consisted of patients with five different MSDs based on the real-world data instead of a simplified homogenous cohort. The subgroup analyses suggested that patients undergoing THR and TKR should be preferably considered for hydrotherapy after the procedures, while for patients with OA, hydrotherapy may not be economically as beneficial as land-based therapy. Although the relative ranking was informative to prioritize resource allocation in a specific jurisdiction, it may not serve as good evidence to exclude OA from target users of hydrotherapy given that cost-effectiveness is only one of the decision-making criteria by clinicians to choose amongst competing treatment alternatives. Limitations of this study Several limitations exist in our study that should be acknowledged. Our model adopted a 3-month time horizon to ensure a valid pooling of societal cost and QALYs of different MSDs. This technical arrangement presented two limitations. One is that the model captured only immediate effect on quality of life which may be unfair to certain conditions. Some conditions may require a longer modelling period to have a comprehensive comparison between hydrotherapy and land-based therapy.14 The other limitation associated with the short time horizon is the over-estimation of QALYs as clinical events such as death were not considered in the model. Data transferability may pose another limitation. The effectiveness data applied in the model were derived from studies conducted in other healthcare jurisdictions based on the assumption that similar utility gains could be achieved by our local hydrotherapy programmes. To ensure internal validity of our results, we sought expert opinion to verify that the utilities were applicable to local context. Lastly, the cost impact of hydrotherapy was not fully reflected in the model. Compared with the study by Cochrane et al.13 our model did not consider other treatment related costs such as medications and devices. Conclusions Our study demonstrated that hydrotherapy was a cost-effective rehabilitation treatment to improve the quality of life for patients with MSDs in Singapore. However, the cost-effectiveness of hydrotherapy was not observed in patients with OA. Funding This work was not supported by any grant or funding. References 1 The Burden of Musculoskeletal Diseases in the United States . Prevalence, Societal and Economic Cost (3rd Edition), the United States Bone and Joint Initiative, NFP (USBJI). http://www.boneandjointburden.org/. (25 September 2017, date last accessed). 2 Bevan S . 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For permissions, please e-mail: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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Journal of Public HealthOxford University Press

Published: Mar 9, 2018

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